Rubber thread and method of making same



March 7, 1939. DRAEMANN 2,149,425

RUBBER THREAD AND METHOD OF MAKING SAME I Filed April 5, 1955 Fig.4-

Fig- 2 in venior:

Max praemann @1 in: final-neg.

Patented 7, 1939 UNITED STATES imam-m rnnnan farm nm'rnon o MAKING same Max Draemann, Cologne-Braunsleld, Germimy Application April 5, 1935, Serial No. 14,136 f In Germany April 17, 1934 11' Claims.

This invention relates to rubber threads of the type used for making various elastic textile materials andthe like.

It is an object of my invention to provide a 5 new type of rubber thread which, while oifering a secure grip to fibrous wrapping materials, is but little susceptible to wear and fissures.

A further object of my invention is to provide a method for producing rubber thread of this 1 type in a simple, cheap and efiicient manner.

Still other objects will become apparent in the course of the following description:

The most usual way of producing rubber thread as used in the manufacture of various elastic tex- 15 tile materials such as braces or elastic bands consists in cutting rubber sheet into suitable strips, the thread having a substantially square cross section. The comparativelysharp edges of such cross sections have been found to be important indispensible, as the four filaments can be united in that they are easily yielding to a slight pressure, thus offering a firm hold to fibrous wrapping materials. On the other hand fissures easily oc cur if the edges are too sharp, and such thread wears out rapidly.

According to the present invention I impart to the rubber thread a cross section having a plurality of indentations or recesses, the peripheral portions or projectionsremaining between such recesses having a circularly rounded outer face.

In many cases a rubber thread having such a cross section may also be defined as one composed of a plurality of round rubber filaments partly united or cemented to each other so as to produce a continuous or coherent cross section.

As the diameters of such individual circular filaments and, consequently, the radii of curvature .of the peripheral projections of the composite rubber thread are comparatively small, these projections remain highly resilient and easily 4o yielding so that fibrous wrappings will be held securely. On the other hand the edges of such rubber thread remain rounded and smooth enough to prevent the formation of fissures.

It is important that the single filaments con- 45 stituting the new rubber thread be either homogeneously united or securely cemented to each other as experience has shown that rubber yarns composed of not interconnected filaments are comparatively weak, as on tension the individual 50 filaments are'elongated to diflerent extents. In the drawing Figs. 1 to 5 are cross sections through various modifications of the rubber thread according to the invention.

Figs. 6, 8, and are front views of three dif- 55 ferent types'of extruding nozzles designed for producing the new type of rubber extruding process? Figs. 7,9, and 11 are sections taken along the lines A-A, of the,nozzles shown inFigs. 6, 8, and 10, respectively. f 3 1 The rubber thread shown in llis composed of four-rounded filaments funited-at their interfaces so as to produce a single coherent cross section having recessesor indentations h. The'outer or peripheral portions of the thread thus formed 10 has radii of curvature identical wlththe radius ofthesinglefilaments. x

The thread is partly .hollow'inview of the empty portion 9' of the cross section, and this feature is also advantageous as-it reduces the 15 weight of rubber for a given length of thread'and also increases the pliability-andsoftness. of the product.

As shown in Fig.2 this featln'e is, however, not

thread by an to form a thread with an uninterrupted solid cross section. c

The star-shaped cross section shown in Fig. 3 is composed of a central filament p united with four circumferential filaments 0 of a smaller di- *ameter. This arrangements of filaments is particularly advantageous in that comparatively little rubber is wanted to produce a rubber thread of a given diameten' Fig. 4 shows a sta -shaped arrangement of five united filaments which are all of the same diameter. The cross section shown in Fig. 5 is composed of seven filaments, but as it does not difier much from the'circumscribed circle, which is moreover touched by the peripheral projections, it oifers the special advantage that it is particularly little suscept'ble of causing disturbances in the uniformity of the lustre of fabrics produced with such rubber thread. Nevertheless the projecting 40 portions of the cross section, due to the comparatively small radii of curvature, are easily yielding and very resilient, thus offering to fibrous wrappings a secure hold which would be entirely missing with a plain round rubber thread ofa similar total diameter. I

In producing the rubber thre d according to my invention I have found it par icularly advan tageous to resort to extruding processes. I may produce the single filaments by extruding an un-' 5o vulcanized rubber composition through nozzles of substantially circular cross section, unite them to form the desired cross section, while they are still sticky, and vulcanize the thread thus obtained.

The rubber composition may be of any convensistencyi so that the.

T cement l0 trudingcomp tional type which includes a certain amount or rubber solvent so a to render the mass sufllclently sticky. Alternativ I may extrude latex-or, similar rubber dis ons having a suitable cone filaments immediately or soon after leaving the nozzles are suificiently V 1 strong to retain their shape. so that they may be led together and caused to unite or coalesce closely in front of the nozzles. g 10 -Instead of producing the composite rubber threadaccording to the invention in an unvulcanized state and vulcanizing it only thereafter I may also produce and vulcanize the individual rubber filaments separately and unite them or [solutionjor'a rubber dispersion. As will be obvious, to those skilled in the art, the individual filaments or thethreaid composed thereof need notbe subjected to a separate vulcanizing step if the exosition consists of one of the wellknown types of vulca'nizedlatex. r g

' A nomle plate suitable for producing rubber thread of the type indicated'in Fig. 1 is shown in Figs. (band 7. In the nomle plate c four conic are arranged close to each other, so that the filaments b, d, e' which slightly swell or expand in front of the outlet of the nozzles, are in touch with each other and coalesce at their interfaces. Whether, or cavities. (g in Fig. 1) are formed depends onti; distan cc of the individual nozzles from each 0 er. v a The nozzles shown in Figs. 8 and 9 substantially correspond to those shown in Figs. 6 and "Zfexsent that the axes l oithe nozzles I: are not in parallel to each other, but inclined so as to meet in front of the nozzle plate. This arrangement greatly facilitates the leading together and uniting of the individual filaments.

This modification enhances the mutual touching and coalescing of theindividual filaments after having left the nozzles.

In order to produce particularly deep grooves in the composite rubber thread suitable recesses 45 may be provided at the outlet face of the nozzle plate. This' is illustrated in Figs. 10 and 11, here part of the front portion of the bridges be een the individual nozzles has been cut away. with a nozzle plate of this type the expansion'of the 50 individual filaments, takes place in the y direction towards the centre of the 65 immediately after their formation.

that the nozzles stance in'the production of threads having at comparatively large diameter, filaments of -a' crossfsection other-than maybe'led together or cemented to each other. Iirthe above description as well as inthe'clalms afllxedtheretd, the. term rubber thread" should 7 up with fibrous material in accorda them toeach other by means of'arubber 3 r filaments. causing such filaments to emerge froni be understood in'its prop r sense so as to ex,- clude rubber band or rubber strip with a width considerably in excess, of its thickness; as such cross-sections are not suitable for being wrapped nce with the object of my invention, and projections and recesses as described'would not exert the intended influence.

I claim:

1. As a new article hread composed of a central rubber filament and of peripheral rubber filaments united with said central filament but otherwise separated from each other 'so as to form a star-shaped arrangement. it I I 2. The method of rubber thread comprising extruding simultaneously along a correspdndlng number of orifices with axes converging -in the direction of extrusion a plurality of rubber theorifices in close vicinity to each other so as to coalesce partly and to form projections of the thread separated from each other by recesses. andassisting said coalescing effect by permitting the filaments to expand partly'in a centripetal direction'before they wholly emerge from the extruding orifices.

'3. As a new articleof manufacture, a-rubber' thread being composed of a homogeneously united filaments and having a cross-section of the form;of a body provided with propectiohs of substantially circular circumference formed by ing a cross-section of the form of afbody pro- .4

' /thread being composed of homogeneously united filaments, each of said filaments having a sub- -opposite radial directions. J1meapart of said filaments, said projections forming recesses between each .other extending in the 'direction of the longitudinal axis of the thread. yd 4. As a new article of manufacture, a rubberthread being composed of individual filaments cemented to each other, said rubber thread havvided with projections of substantially circular circumference formed by a part of said filaments, andsaTd projections forming recesses between each other extending in the direction ofthe longitudinal axis of the thread.

5. As a new article of manufacture,-a rubber thread being composed of individual filaments united by vulcanized rubber, said rubber thread having a cross-section of the-tormpf a body provided with projections of substantially circular circumference formed by a part of said filaments, and said projections forming recesses between each other extending in the direction of the longitudinal axisof the thread. :7 4 6. As a new article of manufacture. a rubber stantlally round cross-section, said rubber thread having a cross-section of the form of a body provided with projections of substantially circular circumference formed by a part of said filaments, and said projections forming recesses between eachother extendingin the direction of the longitudinal axis of the thread. I

7.,As a new article of manufacture, ahollow rubber thread composed of'partlrunited fila-r ments and having a cross-section of the form of a hollowbody provided with projections of substantially circular circumference forming recesses' between each other, said recesses extending in the dire the thread 8. As a new article oi manufacture, a thread being composed of a central rubber filainent and a plurality of rubber filaments surrounding of manufacture a rubber'io ction of the longitudinal axis of :0

said central filament, apart of the cir- 7 being united with said central filament, the other part .of the circumference of each 0! said sur-.

cumierence of each of said surroundingfllaments partly uniting with each other said non-coagulated filaments by their expansion under the pressure'of the extrusion in front of said orifices immediately after their formation to form a rub- V ber thread having a cross-section ofthe shape of a body provided with projections of substantially circular circumference forming recesses between each other.

10m method of making rubber threads comprising the steps of extruding a plastic sticlqr rubber mass through a plurality of adjacent orifices forming a plurality of rubber i ilaments,

partly uniting with each other non-coagueach other.

lated filaments by their expansion under the pressure of the extrusion in front of said oriiices immediately after their formation to form a rubber thread having a cross-section of-the shape of a body provided with projections of substantially circular circumference forming recesses between each other, and 'vulcanizing the rubber thread thus formed.

'1'1. A method of making rubber threads comprisingthe-steps of extruding a plastic. sticky rubber mass through a plurality. of adjacent orifices having converging axes and forming a plurality of rubber filaments, and partly uniting with each other said non-man ated filaments by. their expansion-under the, pressure of the extrusion in front of said orifices immediately I after their formation to form a rubber thread having across-section of the shape of a body 7 provided with projections of substantially circular circumference forming. recesses between I MAxnRAmA1-m 

